Storms in the Mediterranean basin will be rarer but stronger as the effects of warming become more severe, a new study predicts
Ruth Schuster | Feb. 19, 2019 | 2:39 PM

When the 21st century winds down and the world warms, storms in the Mediterranean basin are going to become less frequent — but also more violent and protracted, according to a new climate model published in Geophysical Research Letters.

Based on a climate model called “global coupled,” which factors in the interplay between ocean and land, when a team headed by Spanish researcher Juan Jesus Gonzalez-Aleman of the University of Castilla-la Mancha looks beyond 2080, future “Medicanes” will be much more likely to reach the strength of robust Category 1 storms. Moreover, the storms will stick around longer, pouring down rain and exacerbating the risk of flooding.

Such concern over a Category 1 tempest, the least severe on the scale, would probably make Floridians giggle. But by Mediterranean standards, it would pose an almost unheard-of level of climatic violence, certainly in the sea’s eastern basin.

Why do they predict that “extra-tropical cyclones” typical of the Med region will strengthen? Because climate change is causing global warming, which has been warming the surfaces of the oceans and seas.

So, simply, Gonzales-Aleman explains: “Because sea surface temperatures will increase and the atmospheric environment will be more favorable for them to get stronger,” he tells Haaretz. “It’s like the Mediterranean Sea will be a more tropical-like region.”

Atlantic and Mediterranean hurricanes (and typhoons) are very similar. Both are rapidly rotating systems of thunderstorms swirling around a low pressure-eye, but the storms that normally strike the Mediterranean tend to do damage because of torrential rain and consequential flooding. Violent winds at the surface are rare.

It bears noting that, according to Gonzalez-Aleman’s paper, Atlantic hurricanes and typhoons blow hardest at the surface, but Medicane winds are at their most violent in the upper atmosphere, some 12 kilometers (7 miles) above the earth’s surface. That might help explain why most of the Medicanes experienced in the last 60 years have felt downright balmy compared to full-blown Atlantic hurricanes.

The eye of a Medicane forms at lower speeds compared with hurricanes and typhoons, says the paper, which was written by scientists from both the University of Castilla-La Mancha and Princeton University in New Jersey.

To meet the definition of a Category 1 Atlantic hurricane, a storm must sustain wind speeds of at least 74 miles per hour (119 kph) for at least one minute. Medicanes usually, if not always, max out at half that speed.

Category 5 hurricanes sustain winds of 156 mph and more, which is 251 kmh, which nobody is talking about in the context of the little Mediterranean, certainly not at this stage.

When Medicanes do develop, which is about once or twice a year (or as scientists put it, 1.9 + 1.3) it’s usually in the western and central Mediterranean, around Italy, Spain, Crete and the other Greek islands, although the North African coast is also not immune. More than 600 people died and a quarter-million people were made homeless when a particularly strong howler struck Tunisia and Algeria in September 1969.

For Israel, the main impact so far has been Medicanes that hit somewhere else, giving local surfers a thrill. The shallow, mild Mediterranean is otherwise not known for its breakers. Surfing in Israel is more the art of not falling off your board when some jerk is playing Jaws.

A separate 2017 study of 65 Medicanes between 1947 to 2014, conducted by the University of Athens and the Hellenic National Meteorological Service, found that their frequency spikes in September. That, meteorologists explain, is because the seawater has been warmed throughout the summer, and cold air currents start arriving from the north.

Though Medicanes are extremely rare in summer, and during the period tracked never occurred in June, they can theoretically happen any time of year, scientists have noted. In general, Medicane season begins with a vengeance in September, but their probability remains higher throughout the winter than in spring or summer.

The model predicts that these Medicanes will continue to occur mainly in the autumn. Middle Easterners could be pardoned for hoping that downpours and howling winds would at least alleviate the blistering heat, which is expected to become all the more onerous. Violent storms might not be much of an improvement, however.

Despite wild weather elsewhere in the world, so far, Medicanes have not been observed to be undergoing any remarkable change, Gonzales tells Haaretz. “Indeed, our study suggest that this will not happen until 2080.”

As the world burns

These scientists are peering ahead more than 60 years. Normal weather forecasting for tomorrow is iffy enough. How likely is it that their forecast will be borne out?

“Our model is more accurate because it is global and not regional, and also because it is coupled with the ocean, allowing us to better simulate their interaction with the sea. No studies have been done before with that feature,” Gonzalez-Aleman says. “That is important for medicanes and a better representation of general atmospheric conditions.”

Quite, but under current global policies, we are heading for a radical — but not the most extreme — scenario of global warming of 3 to 4 degrees Celsius above pre-industrial levels by 2100. Between ecological disasters on multiple continents, not confined to Australia and the United States – the ramifications of the changes in climate are becoming clearer by the day.

A study released just this month, in the journal Nature, and a paper in Scientific American, suggest that the water from polar ice melt will disrupt ocean currents as we know and love them, and “will cause extreme weather and unpredictable temperatures around the globe.”

A different study published in Nature Geoscience this January double-checked the estimated thickness of glaciers the world wide, and reports that the estimates had been on the high side, to a significant degree: the world’s glaciers have less ice than had been thought. So for instance, where science had projected that glacial coverage worldwide would halve some time in the 2070s, now they’re thinking this will happen some time in the 2060s.

If not before. Yet another study, released this February by the University of California in Environmental Research Letters, throws yet more doubt on all the climate models to date by pointing at yet another parameter: naturally occurring carbon dioxide and other carbon gases trapped in icy reservoirs atop the seafloor.

As the oceans warmed in history (before the anthropogenic age), the seabed carbon reservoirs released greenhouse gas into the atmosphere. Today the ocean is warming again because of manmade global warming: mostly at the surface, but just give it time. “If undersea carbon reservoirs are upset again, they would emit a huge new source of greenhouse gases, exacerbating climate change,” writes the team headed by Lowell Stott.

The Levant and Middle East are not blessed with glaciers but are is affected by climate changes to their north. So all bets are off, really. But the likelihood of extreme weather, storms that stick around longer and dangerous floods in an otherwise desertifying region are not just a bad dream. They’re already happening.

https://www.haaretz.com/world-news/europe/.premium-hurricanes-to-slam-mediterranean-as-global-warming-ramps-up-1.6940372